Aircraft closed circuit breathing system

ABSTRACT

An improvement is presented in an aircraft oxygen closed circuit breathing system wherein in place of the previously proposed flexible breathing bag rendering the system volume a variable, a compressor is employed converting the system to one having a variable pressure and a constant volume.

O United States Patent 1 3,552,392

[72] Inventors Angelo [56] References Cited Schenm NlTE T PATEN John W. Harrison, Manchester, Mas. U D S ATES TS 2,617,414 11/1952 Hollmann 128/142 [21] App]. No. 741,527 v 3,190,287 6/1965 Mil1er,Jr. 128/191X [22] Filed July 1,1968

3,251,361 5/1966 Rusz 128/188 [45] Famed ml 3 358 683 12/1967 0 r 128/204 [73] Assignee General Em Company 01 em"... I a corporation of New York Primary Examiner-Richard A. Gaudet Assistant Examiner-G. F. Dunne Attorneys-Richard R. Brainard, Paul A. Frank, Charles T. AIRCRAFT CLOSED CIRCUIT BREATHING Watts, Leo 1. Ma Lossi, Frank L. Neuhauser, Oscar B.

SYSTEM Waddell and Melvin M. Goldenberg 3 Claims, 3 Drawing Figs.

128/142, 137/81 1 [51] Int. Cl A 6 1m 1 5/1l 9, ABSTRACT: An improvement is presented in an aircraft ox- A621) 7/02 ygen closed circuit breathing system wherein in place of the i [50] Field of Search 128/204, previously proposed flexible breathing bag rendering the 19l,142.3, 146,146.3,146.4,146.5,146.6,l42.2, 142.5,140,l45.6,203,142147,188,191, 204; 98/15 system volume a variable, a compressor is employed converting the system to one having a variable pressure and a constant volume.

- FL OXYEfA/ A PATENTED JAN SIS?! V 3.5521392 SHEETlOFZ I In yen 1; ans.-

mm w Wi r w 0 av 6 DH M 0 W m /Wm Am MM 0 1 AIRcRAFr CLOSED crRcurr BREATHING SYSTEM BACKGROUND OF THE lNVENTlON Existing breathing systems in aircraftare waste systems in which liquid oxygen is conducted to a heat exchangerand converted to gaseous oxygen. Exhaled gases, though still rich in oxygen, are not refurbished or recycled.

Such refurbishing and recycling of exhaled gases has been proposed, it having been recognized in such proposals that in a closed circuit breathing system means have to be provided to compensate for system volume changes for the safety of the user e.g. the pilot, and to prevent needless expulsion of oxygen from the system during violent aircraft maneuvers. The most significant system volume change requiring compensation is the expansion and contraction of the lungs of the user. Heretofore, it has been contemplated that compensation of system volume changes would be accomplished. by a flexible breathing bag incorporated in the systems, for example, is v shown in Pat. application Ser. No. 615,582 (now US. Pat. No.

3,489,144), Dibelius et al., filed Feb. l3, 1%? and Pat. application Ser. No. 664,875, Dounoucos, flied Aug. 31, 196']. The aforementioned applications have been assigned to the assignee of the instant invention.

in essence, the closed circuit breathing systems described in to allow oxygen to bleed ofi during any climb of the aircraft or to have additional oxygen be drawn from the storage supply during any dive of the aircraft. Repeated climbs and dives would then precipitate a serious loss an'dan unnecessarily high usage rate of oxygen, This, in turn, would require a greater than practical capacity for storage and concentration. Analysis of the problem indicates that in order to satisfy these conditions the minimum volume of the breathing bag (for two users) would have to be greater than liters,'a requirement which (due to space limitations) would considerably limit the number of aircraft to which such systems would be applied.

The art is, therefore, in need of an improvedsystem component in place of the flexible breathing bag, which'occupies a much smaller space.

SUMMARY or THE r vE rioN The aforementioned need in the artis s atisfied by the in- FIG. 3 is a-schernatic representation of atypical compressor In the aircraft oxygen system shown in FIG. I, either air of considerably increased oxygen concentration or substantially pure oxygen is discharged from oxygen concentrator 11 under the control of concentration on-off pressure switch vl2 either for storage under pressure in oxygen container 13 for later use or for direct controlled admission to the cabin breathing system via oxygen admission'control device (loop pressure regulator) 14. This oxygen admissioncontrol device 14 is shown in greater detail in FIG. 2. The transmission of oxygen gas from conduit 16 to conduit lTis controlled by valve element 18. The positioning of valve element ls'relative to valve j seat 19 is dependent upon the pressures in bellows 2! and bellows 22, representing cabin altitude reference unit 23 and volume system utilizing a compressor. The result'is a pressurized system of marked superiority, which provides the additional benefit of automatic pressure breathing. capability wherein the pressure of the oxygen supplied to the 'user is slightly higher thanthe pressure outside the body in order to induce breathing. The space occupied by the compressor is less than 15 percent of the space rquiredjhy the flexible breathing bag. Provision is madefo'r continued short term closed-loop breathing in the event of failure of thealternating current power required for operation of the compressor.

BRIEF DEscRiRnoN OF his DRAWING The exact nature of this invention as wellas ctherbbjects and advantages thereof will be readily apparent from con-- sideration of the following specification relating to the annexed drawing in which:

FIG. 1 is a schematic diagram of a self-contained aircraft v loop pressure reference unit .24, respectively. Lever 26,

pivotally. connected to valve element 18 is pivotally connected at one end to rod 27in cabin altitude reference unit 23 and at the other end of rod 28in loop pressure reference unit 24. The relative upward-downward movements of rods 27, 28, therefore, serve to determine the vertical positioning of valve element 18. 'At the upper end thereof rod 27- is connected to bellows 21 and is positioned thereby while the lower end thereof 1 is connected to calibrated springfl29. The extension or eontraction of bellows2l is dependent upon cabin pressure, bellows 21 being in flowcommunication with the'cabinspace 'via conduit 31. Rod 28, on the other hand, is connected at its lower end to bellows 22. The movement of bellows'22 is deter- "mined by the gas pressure in the closed breathing loop tioned applic'ation'Ser. No. 615,582 or a solid electrolyt e'fuel cell operated in reverse as described in the aforementioned application Ser. No. 664,875. Both of the aforenientierie'd patent applications are incorporated by reference herein.

Makeup oxygen entersthe breathing systemfvia'conduit fl into exhaust line 36 carrying exhaled air from breathing masks 37, 38 worn by pilots, for example, this air'havin'gbeen compressed'by compressor 32. Thispressuriiedexhaled air plus,

makeup oxygen passes to carbon dioxide scrubber 39, wherein the carbon dioxide contentjof the exhaled air is'd epl eted by passageof bo dioxide-gasat a high rate'throu'g'h perms'e'lective membrane 41 Some oxygen is lost fromlthe system at the sametime, b'ut'thje perrnselective'membrane isprope'rly selected such that the depletion' of carbondibxidej occurs 'at a much fasterjrate than is the case with oxygen. The breathing air-purged of CO, to the extent desired exits from CO scrubber 39via conduit' 42.

The rejuvenated breathing through altitude-programmed inhalationvalve 4 3 a'one-w'ay valve which effects a pressure drop "from the slightlyfgreaterloop pressiire to the properpressurefor bteething, In a typical arrangement this pressure difiei'ential is about 5 p.51.

Next the breathing pas; 's to oxygenjserisor detects the presence'of contaminant'gases, usually rn'anifest'as a Jdecr'ease in oxygen con'tent and increase in nitrogen'content.

The condition of purityof the air passing through sensor is expressed in an electrical output signal presented to 'signal comparing device '46. If there is sufiicient-contamination to require purging, signalf'comparator 46' actuates 1 soleneidoperated purging valve 47 to the open pesition permitting gas to leave the closed circuit. The pressure both in the inlet 48 to compressor 32 and downstream of compressor 32 is reduced causing bellows 22 to contract, rod 28 to move down and valve element 18 to move away from valve seat 19 thereby admitting pure oxygen to'the breathing circuit. This admission of V oxygen will continue until the purity of the circulating gas causes sufficient readjustment of the signal from sensor 44 to signal comparator 46 to bring about closure of purge valve 47. Rejuvenated breathing gas of controlled purity is supplied to masks 37 and 38 via conduits 49 and 50, respectively, through the one-way valves 51 and 52, respectively. Exhaled breath is vented from masks 37, 38 via one-way valves 53, 54, sterilizers 56, 57 and conduits 58, 59, which connect to conduit 48. In typical sterilizer construction an activated charcoal filter is employed acting to remove odors and trap bacteria and fungus.

In line 48 are located one-way exhalation valve 61, purge valve 47 and relief valve 62. The exhalation valve 61 serves to isolate the pilotslungs from the relatively low pressure region in line 48 upstream of compressor 32. In the case of two or more people being supplied by the same closed breathing circuit, if all users were to violently exhale at the same time there would be a danger of overrunning compressor 32. Tocounter such a contingency, relief valve 62 is provided. Should the simultaneous exhalation occur this valve 62 would open and release some gas fro'm'line 48 to the cabin.

Exhaledbreath is, therefore, compressed by compressor 32 and additional oxygen is provided as required through line 17; Thereafter, as noted hereinabove the gas passes to CO scrubber 39. The outside surface of membrane 41 receives a circulating stream of air or other gas (circulating means not shown), in order to prevent undue .CO, concentration over the outer surface of the membrane.

Compressor 32 is preferably of the diaphragm-type as is shown in FIG. 3. Whatever unit is employed it should either operate free of oil or be equipped with means for removing oil from the gas stream.

In compressor 32 shown, exhaled breath gas enters from line 48 into annular distribution manifold 63 and passes through the annular opening 64 displacing annular flap valve 65 downward and entering main pump chamber 66. As actuating rod 67 is moved upward by theaction of electric motor 68 by which it is driven, flexible diaphragm 69 isflexed upwards and the gas in chamber 67 is compressed and forced out through flap valve 71 into conduit 36.

in the event of power failure for motor 68, the valving arrangement presents the possibility for short term closed-loop breathing to continue through compressor 32 providing a small emergency breathing bag is provided as shown in dotted lines upstream of compressor 32 and means (not shown) are provided for selectively decreasing the pressure differential set by valve 43. Such a breathing bag would remain collapsed during normal operation of the compressor, because of suction in line 48.

If there is no meansfor selectively reducing the pressure dif ferential introduced by programmed inhalation valve 43 and compressor 32 becomes inoperable, a waste emergency breathing operation will be initiated. As longas there is a supply of oxygen under pressure, oxygen will be supplied to masks 37, 38 via oxygen admission control 14 and exhaled gases will exit via relief valve 62 to' the cabin. If desired, of

course, an emergency supply of oxygen may be provided admissible through the system described herein. Should any breathing'station be unoccupied during flight, means (shutoff valves 72, 73) are provided to prevent unnecessary loss of oxygen from the closed system.

Therefore, a highly desirable variable pressure, constant volume closed circuit breathing system has been developed requiring considerably less space than proposed .vari'able' volume, constant pressure closed circuit breathing systems and providing automatic pressure breathing for users.

We claim:

1. In a closed circuit breathing system for the distribution 'of oxygen to, and waste gases from, the respiratory organs of a vertebrate wherein a respirator adapted to be worn by the vertebrate is, by separate conduits, connected to and in flow communication with an enclosure defined by both impermeable wall area and permeable, nonporous wall area having a co,/o, permeability ratio of at least about 5 whereby exhaled breath from the vertebrate is transmittedfrom said respirator to said enclosure, is depleted in CO content and transmitted back to said respirator in a closed circuit and means are provided in flow communication with said closed circuit for introducing makeup oxygen thereto, the improvement comprising: means forselective operation of said closed circuit either as a variable pressure, constant volume system or as a constant pressure, variable volume system, said means comprising a compressor connected in series in said closed circuit and a flexible breathing bag located in flow communication with said closed circuit upstream of said compressor, said compressor having valve means located therein providing some flow path therethrough during either condition of selective operation.

2. The improvement substantially as recited in'claim 1 wherein the compressor is of. the diaphragmtype.

3. The improvement substantially as-recited in claim 1 wherein a relief valve is provided downstream of the compressor and in flow communication therewith to prevent overrunning of said compressor. 

1. In a closed circuit breathing system for the distribution of oxygen to, and waste gases from, the respiratory organs of a vertebrate wherein a respirator adapted to be worn by the vertebrate is, by separate conduits, connected to and in flow communication with an enclosure defined by both impermeable wall area and permeable, nonporous wall area having a CO2/O2 permeability ratio of at least about 5 whereby exhaled breath from the vertebrate is transmitted from said respirator to said enclosure, is depleted in CO2 content and transmitted back to said respirator in a closed circuit and means are provided in flow communication with said closed circuit for introducing makeup oxygen thereto, the improvement comprising: means for selective operation of said closed circuit either as a variable pressure, constant volume system or as a constant pressure, variable volume system, said means comprising a compressor connected in series in said closed circuit and a flexible breathing bag located in flow communication with said closed circuit upstream of said compressor, said compressor having valve means located therein providing some flow path therethrough during either condition of selective operation.
 2. The improvement substantially as recited in claim 1 wherein the compressor is of the diaphragm-type.
 3. The improvement substantially as recited in claim 1 wherein a relief valve is provided downstream of the compressor and in flow communication therewith to prevent overrunning of said compressor. 